1. Field of the Invention
This invention relates to a novel liquid crystal and a liquid crystal composition containing the same. More particularly it relates to a carbonic acid ester liquid crystal compound having an optically active group and that in an optically active form or in a racemic form as well as a chiral liquid crystal composition containing these.
2. Description of the Prior Art
At present, as to liquid crystal display elements, TN (Twisted Nematic) type display mode has been most broadly employed, but as far as the response speed is concerned, such TN type display elements are inferior to emissive type display elements (such as those of electroluminescence, plasma display, etc.). Although various improvements in this respect have been attempted, it appears that improvement to a large extent has not been achieved. Thus, various liquid crystal display devices based on a different principle from that of TN type display elements have been attempted. As one of such devices, there is a display mode utilizing a ferroelectric liquid crystal (N. A. Clark et al: Applied Phys. Lett., 36, 899 (1980)). This mode utilizes the chiral smectic C phase (hereinafter abbreviated to SC* phase) or the chiral smectic H phase (hereinafter abbreviated to SH* phase) of the ferroelectric liquid crystal, and those having these phases in the vicinity of room temperature are preferred.
As liquid crystal compounds exhibiting a chiral smectic phase, some compounds have already been known (for example, Japanese patent application laid-open Nos. Sho 53-22833/1978, Sho 60-54341/1985, etc.). However, in various respects, there is none exhibiting fully satisfactory properties.